ECHO-PLANAR IMAGING OF THE ABDOMEN

Echo planar imaging (EPI) is an ultrafast magnetic resonance (MR) imag ing method first proposed more than 15 years ago. With EPI, all the in formation necessary to create an image is obtained very rapidly (typic ally on the order of 50-150 ms). Special hardware modifications are, n eeded, particularly in the magnetic field gradients and data acquisiti on systems, to permit such high-speed imaging. In the abdomen, EPI ima ges are insensitive to degradation from breathing or peristaltic motio n. The essentially infinite repetition time and lack of motion-induced blurring can improve lesion characterization compared with standard i maging methods. Segmented EPI permits high-resolution T2-weighted imag es to be acquired within a single breath-hold. Diffusion imaging, whic h was previously restricted to the brain, can now be done in the abdom en because of the relative insensitivity of EPI images to bulk motion. Diffusion imaging of the kidney has been found to correlate with its functional status. By using EPI readouts, MR angiography can be done m ore quickly. Further work is needed to improve the spatial resolution and overcome magnetic susceptibility artifacts, particularly with sing le-shot EPI. Nonetheless, EPI offers considerable potential for improv ed anatomical and functional imaging of the abdomen.